Method and Systems for Processing Text Found in Images

ABSTRACT

An image containing text (e.g., a surveillance camera photo that includes a vehicle license plate) is analyzed to determine the text (e.g., by an OCR technique). The recognized text is then stored in a database. The image is digitally watermarked with an identifier that associates the image with the database location where the text is stored. In addition to surveillance contexts, this technology can be employed in indexing the World Wide Web. Images used in web pages can be watermarked to link to associated text or other data. When the web page is crawled by an indexer, the watermark can be decoded and the associated data repository accessed to obtain information that can augment the web index for that page.

RELATED APPLICATION DATA

This application is a continuation of application Ser. No. 09/670,113, filed Sep. 26, 2000 (now U.S. Pat. No. 7,657,064), the disclosure of which is incorporated herein by reference.

DESCRIPTION

The World Wide Web is a distributed database including hundreds of millions of documents. Search engines such as Alta Vista attempt to index the web based on ASCII text included on each page and on associated meta tags. Increasingly, however, text information is present on the Web in the form of text images. Known search engines are unable to make use of text presented in this form.

One approach to this problem is discussed in Lopresti et al, “Locating and Recognizing Text in WWW Images,” Information Retrieval, vol. 2, no. 2-3 p. 177-206, 2000, and involves a procedure based on clustering in color space followed by a connected-components analysis. Character recognition is performed using polynomial surface fitting and “fuzzy” n-tuple classifiers. While suitable for some applications, such techniques are too computationally intensive and imprecise for widespread use.

In accordance with one embodiment of the present invention, an image containing text is digitally watermarked with an identifier. The identifier serves as an index to a database record where additional information about the image, including keywords or full text of the included text, are provided. To obtain the associated data, a search engine web crawler or other process can download an image, apply a watermarking detection procedure, use an identifier thereby obtained to index a database, and access keywords or full text represented in the image from the indexed database record.

The text can be entered in the database using various known methods. One is to have the text manually coded by a clerical service. Another is to apply an automated OCR process to the image data, such as that detailed by Lopresti. Once the text is once thereby developed, it can be made quickly available repeatedly thereafter by reference to the associated database record.

The database can be conventional, and is preferably accessible over the internet. A suitable database system is disclosed in copending application Ser. No. 09/571,422, filed May 15, 2000 (now U.S. Pat. No. 6,947,571). A variety of watermarking techniques are known. An illustrative set of techniques that can be employed in this application is disclosed in copending application Ser. No. 09/503,881, filed Feb. 14, 2000 (now U.S. Pat. No. 6,614,914). The disclosures of these applications are incorporated herein by reference.

The technology disclosed herein finds myriad applications. As noted, one is in the indexing of a collection of electronic documents (e.g., web pages). An index augmented by the results of such a procedure is generally more useful than such an index without augmentation.

Another application is in the use of webcams, or security monitoring cameras. Certain image frames from such sources (e.g., one every minute, or one every second, etc.) can be analyzed for textual information (e.g., license plate markings, superimposed date data), and the textual information stored. The image data is watermarked, with the watermark indicating the repository of the corresponding textual information.

Still another application is PDF documents or fax data files. (While some PDF files include corresponding ASCII text data, most do not.) The file data can be applied to an OCR engine, and the resulting text stored in a database. The PDF or fax data file can be slightly altered to impart a watermark—the watermark again serving to point to the repository of the corresponding text information.

Yet another application is in photocopiers. Again, the textual content is extracted from the scanned image of the original document. In this case the paper photocopy output (or a corresponding digital file) is altered in slight respects to encode a watermark. The watermark points to the text data repository.

While the illustrative embodiment particularly considered watermarks that convey an index to a remote database, other arrangements are naturally possible. For example, the watermark can directly encode the fulltext or keywords (forms of metadata).

Similarly, while the illustrative embodiment particularly considered imaged text in image files, the same principles can be applied more widely. For example, all metadata associated with an image through a watermark can be employed in compiling an index of the web or other collection of content data—not just included text (e.g., names of persons and places, dates, times, and other more application-specific metadata). Moreover, such techniques are not just limited to images. Other forms of content, including video and audio, can be watermarked, and the metadata thereby associated with the content can be used for web indexing and other purposes. 

1. A method comprising: receiving data corresponding to an image, the image including a depiction of text; recognizing at least some of said depicted text; and steganographically encoding a digital watermark in said image, said steganographically encoded digital watermark comprising a visually imperceptible carrier of information rather than a conspicuous carrier of information, such as a barcode, said digital watermark serving to associate said image with said recognized text.
 2. The method of claim 1 in which said recognizing includes recognizing by an automated OCR process.
 3. The method of claim 1 that includes storing said recognized text in a data repository, and wherein said watermark serves as to associate said image with said stored text.
 4. The method of claim 1 wherein said digital watermark serves to directly encode at least a portion of said recognized text in said image.
 5. The method of claim 1 in which said encoding follows said recognizing.
 6. A method comprising: receiving an electronic document, the document comprising a graphical representation of text, but not including ASCII data corresponding thereto; analyzing said document for text information using an OCR process; and digitally watermarking said electronic document with a visually imperceptible marking that conveys plural bits of information; wherein said digital watermark associates the electronic document with the text information.
 7. The method of claim 6 in which the electronic document comprises FAX data.
 8. The method of claim 6 in which the electronic document comprises a PDF document.
 9. The method of claim 6 in which receiving an electronic document comprises scanning a paper document on a platen, and producing graphical data corresponding thereto.
 10. The method of claim 6 wherein said digital watermark directly encodes the electronic document with at least some of said text information.
 11. The method of claim 6 that includes storing the text information in a data repository, and wherein the digital watermark associates the electronic document with said information in the data repository.
 12. A system comprising: a scanner for producing scan data corresponding to an original document; an OCR engine for recognizing text from said scan data; and a watermarker that alters an output from said apparatus to steganographically encode a digital watermark therein, the watermark comprising a visually imperceptible carrier of information rather than a conspicuous carrier of information, such as a barcode, the watermark serving to associate said output with said stored text.
 13. An apparatus according to claim 12 wherein the output comprises a hardcopy page, and said watermark serves as a pointer to a memory location in which said recognized text is stored.
 14. An apparatus according to claim 12, wherein the output comprises a hardcopy page, and said watermark serves to directly encode at least a portion of said recognized text in said output.
 15. A method of building an index to a collection of web pages by reference to text and meta tags found therein, the method including the acts: downloading an image from one of said web pages; decoding a steganographically encoded digital watermark from the downloaded image; through use of said decoded digital watermark, obtaining text associated with said downloaded image; and augmenting the index in accordance with said obtained text.
 16. The method of claim 15 in which the decoded digital watermark includes a database reference, and the method includes using said reference to obtain information from an associated database record. 